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Biological Biological Phosphorus RemovalPhosphorus Removal

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PhosphorusPhosphorus is an essential nutrient for plants and animals in the form of ions PO43- and HPO42-

It is a part of DNA-molecules, molecules that store energy (ATP and ADP) and fats of cell membranes. Phosphorus is also a building block of certain parts of the human and animal body, such as thebones and teeth.

Can be found on earth in water, soil and sediments.Cannot be found in air in the gaseous state because phosphorus is usually liquid at normal temperatures and pressures. It is mainly cycling through water, soil and sediments. In the atmosphere phosphorus can mainly be found as very small dust particles.

Polyphosphates are used industrially to bind metals, such as in some laundry detergents

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Phosphorus and nitrogen in water resources stimulate growth of algae and other photosynthetic aquatic life, which lead to accelerated eutrophication of lakes and other natural waters

Eutrophication causes : Increased water purification costs ,Interference with the recreational value of water, Health risks to both humans and livestock. excessive loss of oxygen resources, andundesirable changes in aquatic populations.

The EU Urban Wastewater Treatment Directive will require an effluent standard of no more than 1mg/l phosphate for large treatment works

1/30/2006 Biological Phosphorus Removal 4Toba Lake in North-Sumatera, Indonesia

1/30/2006 Biological Phosphorus Removal 5Eutrophication beginning in Toba Lake

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Biological Phosphorus removal (BPR) from domestic and industrialwastewater is a key factor in preventing eutrophication of surface watersand one of the most economical and efficient methods for phosphorus removal.

BPR is achieved by :growing microorganisms that are capable of storing phosphorus intracellularly as polyphosphate.

The growth of phosphorus-accumulating organisms (PAOs) is favored by subjecting the activated sludge to a cycle of anaerobic and aerobic conditions

Phosphorus is then removed by wasting excess sludge.

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Parameters that have been used to evaluate the feasibility of BPR include :

ratios of biochemical oxygen demand (BOD5) or chemical oxygen demand (COD) to phosphorus (P) total Kjeldahl nitrogen (TKN) to COD.

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ProcessEnhanced biological phosphorus removal (EBPR) from wastewater involves mixing the influent wastewater with settled microbial biomass enters the anaerobic selector where chemically bound oxygen in the form of nitrates is removed

The microorganisms have the ability to store energy in the form of polyphosphate chemical bonds .Some of these microorganisms are called polyphosphate accumulating organisms (PAOs)

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In the anaerobic zone, where substrate (BOD) concentration is high, the absence of oxygen causes the micro organisms to release the stored intracellular polyphosphates by decompositionto simple orthophosphate

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The decomposition of polyphosphate to orthophosphate results in an increase of soluble phosphorus in the mixed liquor and also releases energy. The energy is used by the micro organisms to transport soluble BOD through the cell wall and to store the soluble BOD inside the cell .Thus, the BOD concentration in the mixed liquor is reduced without the use of oxygen

In the oxic phases of the process, the organisms, in the presence of dissolved oxygen :

convert the stored BOD to CO2, water, and increased cell mass

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A portion of the energy from this reaction then goes to recreating the intracellular polyphosphate using the orthophosphate released in the anaerobic zone

Since new cells are grown, the amount of phosphate removed from solution is greater than that previously solubilized in the anaerobic zone, thus providing for a net phosphate removal

Phosphorus is removed from the system as a fixed biological material in the waste sludge. The amount of phosphorus in the sludge will be dependent upon the amount of BOD and phosphate in the influent and the volume of sludge produced.

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The phosphorus cycle

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PolyphosphatePolyP is readily degraded by the action of a number of enzymes. PolyP may subsitute for ATP in various kinase reactions with, AMP, ADP and glucose and for other sugars, nucleosides, and proteins (Kornberg et al., 1999) (Kulaev & Kulakovskaya, 2000).

Inorganic polyphosphate (polyP) is a linear, unbranched polymer of orthophosphate residues linked by phosphoanhydride bonds

PolyP is widespread in bacteria and yeasts and has been found in plant and animal cells PolyP was first found in yeast cells by Liebermann (1888).

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Microorganisms in BPR process

No polyphosphate-accumulating organisms isolated from enhanced biological phosphorus removal have been able to depict the general metabolic behavior observed for activated sludge . Among them are :

Acinetobacter sppLampropedia spp .Microlunatus phosphovorus , and Tetrasphaera spp .

By using a clone library and fluorescent in situ hybridization techniques, it was shown that bacteria related to the Rhodocyclus group ("Candidatusaccumulibacter phosphatis") were widespread in laboratory-scale enhanced biological phosphorus removal reactors, with extremely efficient P removal

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•Some microorganisms store phosphate as polyphosphate.

•Research now at pilot scale with Severn Trent Water Ltd, Yorkshire Water plc, and Northern Ireland Water Service.

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Biological phosphorus removal by a pure culture of Lampropedia spp

Lampropedia spp. is a gram-negative, Neisser-positive coccus that was isolated from EBPR (enhanced biological phosphate removal) activated sludge laboratory plants operating on dairy and piggery wastewaters.

Lampropedia spp. in pure culture (Blu Nilo stain)

Stante L., Cellamare C. M., Malaspina F., Bortone G. and Tilche A.ENEA - Sezione Depurazione e Ciclo dell'Acqua - Via Martiri di Monte Sole, 4 I-40129 Bologna - Italy

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A bacterium belonging to the genus Lampropedia isolated from EBPR activated sludge has been studied for its capacity of performing enhanced biological phosphate removal. Acetate uptake, PHB formation and phosphate release in anaerobic conditions as well as phosphate uptake and PHB consumption in aerobic conditions have been recorded. but cell phosphorus fractionation analyses demonstrated a cyclic increase and decrease of the poly-P fraction from aerobic to anaerobic conditions. All these evidences allow to conclude that Lampropedia spp. can be classified as a poly-P accumulating microorganism.

Lampropedia spp. in activated sludge (Neisser stain, white bar is 10 µm)